The present invention relates to a side airbag apparatus that is deployed and inflated at a side of an occupant of a vehicle.
When an impact that is equal to or greater than a predetermined value is applied to a body side portion of a vehicle because of a collision (side collision), a typical side airbag apparatus deploys and inflates an airbag at a side of an occupant to reduce the impact applied to the occupant, thereby protecting the thorax or lumbar region of the occupant. Such side airbag apparatuses have been disclosed in, for example, Japanese Laid-Open Patent Publication No. 2004-189187. The side airbag apparatus has a belt-like tether that connects a front end and a rear end of the interior of the airbag. A part of the tether in the longitudinal direction is folded such that a loop having a predetermined width and overlapped portions is formed. The overlapped portions of the loop are sewn to each other to form a breakable portion.
When the air bag is deployed and inflated, tension of the tether limits the amount of expansion along the fore-and-aft direction of the vehicle, while increasing the amount of expansion along the lateral direction of the vehicle to protect an occupant. When, in this state, the tether breakable portion is broken as the pressure in the airbag increases, the tether is extended to be longer. This increases the expansion amount of the airbag along the fore-and-aft direction. At the same time, the expansion amount along the lateral direction of the vehicle is reduced so that the pressing force of the airbag applied to the occupant is reduced.
According to the side airbag apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-189187, the behavior of the airbag during deployment and inflation is controlled by changing the tension during inflation of the airbag regardless of the sizes of the occupant. That is, such an airbag apparatus still has plenty of room for improvement in terms of improved protection of occupants in accordance with the size of the occupant.